Beyond Simple AGN Unification with Chandra-observed 3CRR Sources at 0.5 < z < 1

Joanna Kuraszkiewicz, Belinda J. Wilkes, Adam Atanas, Johannes Buchner, Jonathan C. McDowell, S. P. Willner, Matthew L. N. Ashby, Mojegan Azadi, Peter Barthel, Martin Haas, Diana M. Worrall, Mark Birkinshaw, Robert Antonucci, Rolf Chini, Giovanni G. Fazio, Charles Lawrence, Patrick Ogle

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Low-frequency radio selection finds radio-bright galaxies regardless of the amount of obscuration by gas and dust. We report Chandra observations of a complete 178 MHz-selected, and so orientation unbiased, sample of 44 0.5 < z < 1 3CRR sources. The sample is comprised of quasars and narrow-line radio galaxies (NLRGs) with similar radio luminosities, and the radio structure serves as both an age and an orientation indicator. Consistent with Unification, intrinsic obscuration (measured by NH, X-ray hardness ratio, and X-ray luminosity) generally increases with inclination. However, the sample includes a population not seen in high-z 3CRR sources: NLRGs viewed at intermediate inclination angles with NH < 1022 cm−2. Multiwavelength analysis suggests these objects have lower L/LEdd than typical NLRGs at similar orientation. Thus both orientation and L/LEdd are important, and a “radiation-regulated Unification” provides a better explanation of the sample’s observed properties. In comparison with the 3CRR sample at 1 < z < 2, our lower-redshift sample shows a higher fraction of Compton-thin NLRGs (45% vs. 29%) but similar Compton-thick fraction (20%), implying a larger covering factor of Compton-thin material at intermediate viewing angles and so a more “puffed-up” torus atmosphere. We posit that this is due to a range of L/LEdd extending to lower values in this sample. In contrast, at high redshifts the narrower range and high L/LEdd values allowed orientation (and so simple Unification) to dominate the sample’s observed properties.
Original languageEnglish
Article number134
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 3 Jun 2021

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  • active galactic nuclei
  • quasars
  • radio loud quasars
  • x-ray quasars


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